1. Field of the Invention
This invention relates to a process for the reclamation of scrap polyacetal resins. The scrap material is treated in a manner that avoids undesirable loss of certain physical properties so that the reclaimed material may be reused to make acceptable products.
2. Description of the Prior Art
It has long been an economic practice in the plastics industry to reclaim, when feasible, thermoplastic synthetic resinous materials so that they may be reused. Typically, the scrap materials are screened to remove extraneous dirt, ground to a convenient size, and meltmixed in an extruder. The extrudate is granulated to form a useful feed for an extruder, injection molding machine, or other plastic thermoforming device.
Sometimes the physical properties of the polymers are adversely affected when they are reprocessed, but there are many applications in which reprocessed polymers will serve quite adequately. When the physical properties of the reprocessed polymers fail somewhat to meet minimum standards for a given application, it is a known technique to blend the reprocessed polymers with virgin polymer. In many instances, the contribution of the virgin material will bring the physical properties of the mixture up to meet the required specifications.
In the case of polyacetal polymers, which are the subject matter of this invention, one of the important physical specifications to meet is that of an elongation at break of at least 30%, as defined in Federal Specification No. L-P-392A. It has been found that when polyacetals are reclaimed as outlined above, this specified elongation cannot be achieved. Still further, this desideratum still cannot be achieved even when as much as 60% virgin polymer is mixed with the reclaimed scrap material.